Sleep disturbances affect 10 to 20 percent of the general population and represent a major public health challenge. Revealing novel neurotransmitter systems and structures that are involved in sleep regulation will significantly extend our understandings to this essential physiological function. In addition, it will lead to potential therapeutic targets for various sleep disorders or disturbances such as insomnia, excessive daytime sleepiness, sleep apnea and narcolepsy. Neuropeptide S (NPS) and it receptor are a newly discovered neuropeptide system that promotes arousal and wakefulness. Our previous studies have shown that central administration of NPS dramatically induces wakefulness, suppresses all stages of sleep and reduces the transitions between different stages of sleep and wakefulness. Our core hypothesis is that neuropeptide S is an important endogenous regulator of sleep and wakefulness and modulates the activity of arousal center. The long term objective is to further investigate the roles of NPS system in the regulation of sleep and wakefulness. In this proposal, we will investigate three specific aims. (1) To determine NPS peptide, precursor and receptor mRNA concentrations during the light/dark cycle and after sleep deprivation. We will monitor the expressions of NPS peptide, NPS precursor and receptor mRNA contents at different circadian times and in conditions of constant darkness and after sleep deprivation. (2) To determine whether local injection of Neuropeptide S in different brain areas affects sleep architecture and homeostasis. Does local injection of NPS at picomolar doses in three brain regions (A) lateral hypothalamus, (B) tuberomammillary nucleus (TMN) and (C) laterodorsal tegmental nuclei (LDTg) also induce wakefulness and suppress REM and NREM sleep? These three brain regions are proposed because they all express high level of NPSR mRNA and receive intense NPS fiber innervations. In addition, they are brain regions that play important roles in the regulation of vigilance state. These experiments will determine whether NPS acts in neuronal circuits involved in waking and REM sleep, and will increase our understanding on the interaction of NPS with other arousal networks. (3) To determine the consequences of NPS receptor deficiency in sleep architecture. NPS receptor KO mice have recently been generated. We will characterize the sleep parameters of NPSR KO mice under baseline conditions and after sleep deprivation. As we have learned from other peptidergic systems, the data obtained under this aim, if successful, will unequivocally prove that the NPS system is an important component of the circuitry that modulates sleep and wakefulness. [unreadable] [unreadable] [unreadable]